The proper irrigation of soil or other plant growing medium is important in achieving optimal conditions for successful plant culture. In my U.S. Pat. Nos. 3,220,144 and 3,193,970 apparatus is disclosed for providing control and regulation of water appropriate in the case of a single plant. In my U.S. Pat. No. 3,778,928 an irrigation system is disclosed appropriate for controlling irrigation to a plurality of plants in individual containers disposed on a common support such as a bench used in a greenhouse. In my U.S. Pat. No. 4,001,968 I disclose a further improvement in a system for the subirrigation of soil in plant containers characterized by the employment of a capillary sheet having a multiplicity of substantially evenly spaced capillary openings therein overlying a water receptive material which preferably is in the form of the silica sand catalyst sheet that is more particularly described in said U.S. Pat. No. 4,001,968 and that is characterized by a plastic sheet having an adherent continuous coating approximately 1 grain in thickness of silica sand particles essentially in the range from abut 0.002 mm to about 0.25 mm that are interspersed with a network of capillary spaces conductive to lateral spreading of water therealong. Conditions providing excellent results in accomplishing subirrigation are afforded by the method and means disclosed in my U.S. Pat. No. 4,001,968. However, in order to attain the advantage of the silica sand catalyst sheet described in my patent the sheet must be manufactured by the application of the silica sand particles to an adhesive surface presented by a plastic sheet. This requires the use of apparatus appropriate for the purpose and the supply of silica sand particles having the requisite dimensional characteristics. Accordingly, the silica sand catalyst sheet contributes significantly to the overall expense of an installation utilizing and comprising the subirrigation system disclosed in my U.S. Pat. No. 4,001,968.
It is an object of this invention to provide a subirrigation system and method which successfully provides water to soil in plant containers resting on the capillary sheet hereinabove referred to without the employment of the silica sand catalyst sheet for accomplishing capillary travel under the capillary sheet into the area of the capillary sheet in contact with the bottom of a plant container.
It is a further object of this invention to provide a subirrigation system which can be successfully employed and which may be afforded without the expense incident to the preliminary formation of the silica sand catalyst sheet.
Further objects of this invention relate to the provision of an improved tray for supporting plant containers for accomplishing subirrigation which utilizes the improvement of this invention and also is of improved dual bottom construction.